Novel photographic products, processes, and compositions



Oct. 22, 1963 M. GREEN ,1 8

NOVEL PHOTOGRAPHIC PRODUCTS, PROCESSES AND COMPOSITIONS Filed Aug. 17, 1959 SUPPORT no I /PHOTOSENSITIVE LAYER I2 -PROCE$S|NG COMPOSITION l3 lMAGE-RECElVlNG LAYER 14 su pom FlG.l

-SPREADER SHEET ssms COMPOSITION LAYER IMAGE-RECEIVING LAYER SUPPORT FIG .2

INV EN TOR.

ATTORNEYS United States Patent NGVEL PHQTGGRAPEHC PRGDUCTS, PRGQEd-illlfi,

AND CQMPOfilTlQNS Milton Green, Nev/ton Highlands, Mesa, assignor to olaroid Corporation, Cambridge, Mass, a corporation of Delaware Filed Aug. 17, 1959, Ser. No. 834,262 6 illaims. (Cl. 96-29) The present invention relates to photography and more particularly to compositions, products, and processes useful in the development of selectively photoexposed photosensitive silver halide elements, and especially to compositions and products useful in difiusion transfer processes, particularly in high speed diffusion processes wherein a silver halide photosensitive emulsion has been underexposed in relation to its A.S.A. exposure index, that is, to processes for deriving useful photographic transfer prints from latent images formed at low exposure levels.

in diffusion transfer processes, for the formation of positive silver images, a latent image contained in a selectively photoexposed photosensitive silver halid emulsion is developed. Almost concurrently therewith a soluble silver complex is obtained by reaction of a silver halide solvent with the unexposed and undeveloped silver halide of said emulsion. Preferably, the photosensitive silver halide emulsion is developed with a processing composition in a viscous condition which is spread between the photosensitive element comprising the silver halide emulsion, and a print-receiving element comprising, preferably, a suitable silver precipitating layer. The processing cornpos-i tion effects development of the latent image in the emulsion and substantially contemporaneous therewith forms a soluble silver complex, for example, a thiosulfate or thiocyanate complex, with undeveloped silver halide. This soluble silver complex is, at least in part, transported in the direction of the print-receiving element and the silver thereof is largely precipitated in the silver precipitating layer of said element to form the desired positive image therein.

High speed dilfusion transfer processes are generally of the type in which, for example, a silver halide stratum containing a latent image formed at a low exposure level and an image-receiving stratum, in superposition, are subjected to a processing composition containing a highly energetic silver halide developing agent and a silver halide solvent in order to form a silver transfer print in and/ or on the image-receiving stratum. The silver halide developing agent serves to reduce photoexposed silver halide to silver in the photosensitive emulsion stratum. The silver halide solvent reacts with unreduced silver halide to form the aforementioned soluble silver complex which, in turn, is reduced in the presence of the image-receiving stratum to form the desired positive print. The photo sensitive stratum may be subsequently dissociated from the image-receiving stratum. In accordance with a preferred embodiment of the present invention, the silver halide stratum may be underexposed in relation to its rated A.S.A. exposure index and the silver halide developing agent is specifically selected from the class hereinafter set forth.

Preferably, the image-receiving strutum is in such condition as to cause silver reduced there, in comparison with silver reduced in the photosensitive silver halide stratum, to possess very high covering power, that is, opacity per iven mass of reduced silver. This high covering power is achieved by accumulating the silver deposited in the silver-receptive stratum in unsually dense masses, for example, by minimizing the thickness of the stratum in which the silver-receptive material is contained.

The high speed diffusion transfer processes set forth herein provide readily available and uniquely simple proc- 3, l Patented Oct. 22, 1963 esses for producing satisfactory high quality of good resolution and trivial granularity at low illumination levels, for example, at overall exposures that are equivalent to A.S.A. exposure indices of 1,000 and up.

Accordingly, objects of the present invention are to provide: novel products, developer compositions, and processes employing such products and developer compositions, for the development of selectively photoexposed silver halide emulsions; novel products and developer compositions useful in high speed diffusion transfer processes wherein a selectively photoexposed silver halide emulsion has been substantially underexposed in relation to its A.S.A. exposure index; and to employ, in processes of the aforementioned type, a silver halide developing agent selected from the class hereinafter set forth.

Other objects of the invention will in part be obvious and Will in part appear hereinafter.

The invention accordingly comprises the several steps and the relation and order of one or more of such steps with respect to each of the others, and the products and compositions possessing the features, properties and the relation of elements which are exemplified in the following detailed disclosure, and the scope of the application of which will be indicated in the claims.

For a fuller understanding of the nature and objects of the present invention, reference should be had to the following detailed description taken in conjunction with the accompanying drawing wherein:

FIGURE 1 is a diagrammatic enlarged cross-sectional view illustrating the association of elements during one stage of the performance of a diffusion transfer process,

for the production of positive silver prints, the thickness of the various materials being exaggerated; and

FIG. 2 is a view similar to that of FIGURE 1 illustrating the association of elements during one stage of the performance of another diffusion transfer process, for the production of positive silver prints.

A novel class of silver halide developing agents has been discovered which may be represented by the formula:

7 wherein R is an alkyl group comprising from 1 to 4 carbon atoms such as methyl, ethyl, isopropyl, etc., or an alkoxy group comprising from 1 to 5 carbon atoms such as methoxy, ethoxy, isopropoxy, etc., R is an alkyl group comprising from 1 to 4 carbon atoms, an alkoxy group comprising from 1 to 4 carbon atoms, or where R is an alkoxy group, R may comprise hydrogen; and both R and R comprise not more than 5 carbon atoms.

The developing agents of the present invention may be employed in the form of their acid addition salts, such as the hydrochloride.

It will be recognized that the amino group may be substituted where desired, for example, by a lower alkyl group such as a methyl group.

The following compounds are examples of silver halide developing agents within the scope of the present invention:

NH: (1) 4-amino-2-methoxy-G-methyl-phenol CIIaO-k I O CH:

(3) lamina-2,G-dimetl10xy-pheuol NH: (4) d-amino-2-ethoxy-G-rnethyl-phenol H (M QGHB (5) 4-amln02-methy16-propyl-ph enol NH: (6) 4-amino-2-but0xy-pheno1 (7) -amino-2-ethoxy-pl1enol OCH (8) 4-an1ino-2methoxy-pl1eno1 CH CH3 Syl'zthesis 0 4-AmiIw-Z-Methoxy-G-Mezlzyl-Phcuol Hydrochloride A. PREPARATION OF Z-METHOXYA-NITRO-PHENOL A mixture of grams of Z-amino-S-nitroanisole, 100 grams of sodium hydroxide, and 900 cc. of water was reiluxed 30 hours, then allowed to cool overnight. The rod crystals that separated were collected, dissolved in 3 liters of hot water, and this solution of the sodium nitromethoxyphenoxide acidified with concentrated hydrochloric acid. The yellow precipitate of the phenol that came down was filtered off, dried, and crystallized from benzene to give yellow needles, M.P. 9899 C. Concentration of mother-liquors gave additional crops of usable material. [Yield=96%.] Ref.: Drake, Harris, and Jaeger, J.A.C.S. 70, (1948).

B. PREPARATION OF G-(DIMETHYLAMINOMETHYL)-2- METHOXYA-NITRO-PHENOL To a gently refluxing solution of 14.5 grants of 2- methoxyl-nitro-phenol, 45 cc. of ethanol, and 17.5 grams of 25% aqueous dirnethylamine was slowly added 8 grams of 37% aqueous formaldehyde. The mixture was refluxed one hour on the steambath, then allowed to cool overnight. The yellow crystals that separated were filtered off and washed with ethanol, then with ether, and air-dried. The product melted at C., with decomposition, and was used without purification in the following step. [Yield was 91%.]

C. PREPARATION OF 4-AMINO-2-METHOXY-aPHENOL HYDROCHLORIDE A mixture of 13.3 grams of 6-(dimethylaminomethyl)- 2-rnethoxy-4-nitro-phenol, 125 cc. of 95% ethanol, and 17.5 cc. of 3 N hydrochloric acid was heated on the steambath until solid was completely dissolved. The solution was cooled, saturated with nitrogen, and 4 grams of 10% palladium on barium sulfate added. The mixture was then hydrogenated on a standard Parr apparatus under 30 psi. of hydrogen. Uptake of hydrogen was complete in 25 minutes, the drop in pressure corresponding stoichiometrically to 100% nitro reduction plus 80% debenzylation. The reduction mixture was acidified immediately on opening with 10 cc. of concentrated hydrochloric acid, and catalyst was filtered off. The filtrate was concentrated in vacumn to about /5 its original volume, at which point white crystals began to separate. 50 cc. of concentrated hydrochloric acid was added, and the mixture was then chilled and filtered. The precipitate was washed with acetone, then with ether. The product melted at 267 C. with decomposition. [Yield was 69%.]

Analysis-Calculated for C H CINO C 507; H=6.4; 01:18.7; N:7.4. Found: C=50.6; H=6.4;

EXAMPLE 2 Synthesis of 4-AminO-Z-Eth0xy-6-Methyl-Pl1en0l A. PREPARATION OF 6-(DIMETHYLAMINOMETHYL)-2- ETHOXY-PHENOL To a mixture of 55 grams of o-ethoxy-phenol and 72 grams of 25% aqueous dimethylamine was added 32.8

grams of 37% aqueous formaldehyde at 20 C. over a time interval of 10 minutes. The temperature of the mixture was allowed to rise to 50 C., and then dropped indices and diffusion transfer exposure indices can be readily established by obtaining a standardized silver transfer positive and determining the illumination, by measuring with an exposure meter calibrated according to an A.S.A. standard which includes a computer in which has been entered the shutter duration and f-stop of the camera, found necessary to provide the standard transfer print.

in the subsequent discussion, the term. ASA. exposure index is intended to signify the exposure index determined in accordance with the aforementioned Ameri can Standards Association specifications. The term diffusion transfer exposure index is intended to signify, in reference to diffusion transfer processes, or the materials used therein, the exposure index as determined in the aforementioned manner. Both designations, in one sense, serve the same purpose. The ASA. exposure index of the negative is based upon the exposure to which the negative must be subjected in order to obtain a good photograph. of a predetermined subject by conventional processing, whereas the diffusion transfer exposure index is based upon the exposure to which a negative for use in a silver diffusion transfer process must be subjected in order to obtain a good positive by that process. Both, therefore, are direct guides to the exposure setting which must be made in a camera in order to obtain proper exposure. Nevertheless, the two definitions of exposure must be carefully distinguished from each other because, although the A.S.A. exposure index is related qualitatively to the production of a positive of high quality, it is a term which describes the character of a negative material. This negative material, nevertheless, may be employed, for example, in a silver diffusion transfer process of the present invention to effect a diffusion transfer exposure index vastly different from the A.S.A. exposure index of the negative material. In the novel diffusion transfer processes of the present invention, a positive print of satisfactory high quality is produced from a negative material subjected to exposures less, in some cases many times less, than recommended by its rated ASA. exposure index. Such an exposure provides a latent image having a density gradient confined to the low exposure or toe region of the negative materials characteristic curve.

Referring now to the drawing, FIGURE 1 illustrates one assemblage and process of the present invention in the performance of a diffusion transfer process for the production of positive silver prints. As depicted in the drawing, an aqueous alkaline fi-uid layer 12 of a silver halide developing agent chosen in accordance with the present invention and a suitable silver halide solvent are spread between photosensitive emulsion layer 11 which is superposed on support in and image-receiving layer 13 which is affixed to support lever 14. l rnage receiving layer 13 preferably contains silver precipitating agents or nuclei such as the silver precipitating nuclei disclosed in U.S. Patent No. 2,698,237. Support layer 14 may comprise an opaque material where a reflection print is desired or may comprise a transparent material where a transparency is desired.

Fluid layer 12 may be obtained by distribution of the processing composition in a substantially uniform manner between photosensitive emulsion layer l1 and imagereceiving layer 13 for example, in accordance with the procedures disclosed in U.S. Patent No. 2,543,181. For example, one or more rupturable containers may be attached to either photosensitive emulsion layer 11 and/or image-receiving layer 13 such that upon superposition of the respective layers Ill and 13 said container or containers are so positioned as to be capable, upon rupture, of releasing their contents in a substantially uniform layer between and in contact with the opposed surface of each of said layers. Rupture of the container or containers and spreading of the contents thereof may be 8 accomplished, for example, by compression between a pair of opposed, suitably gapped, rollers.

For clarity, the particular developer selected, the degree to which the photosensitive layer is exposed, and the character of the silver-receptive layer will be described in detail hereinafter.

The processing composition preferably comprises a film-forming transfer processing com-position. it may comprise, for example, one or more of the previously enumerated developing agents of the present invention, an alkali such as sodium hydroxide, a silver halide complexing agent such as sodium thiosulfate, and a high molecular weight film-forming thickening agent such as sodium carboxy-methyl cellulose. All these materials are preferably in aqueous solution. These photographic agents are preferably contained in solution in the processing composition prior to the spreading thereof as layer 12, but they may be in part or in whole added to the processing composition as it is spread between the photosensitive emulsion ll and image-receiving layer 13, said agents being so located on, in, or adjacent to a surface of one or both of said layers as to be dissolved by or otherwise interacted with the liquid agent when the latter wets said layers.

In carrying out the aforementioned transfer process, the photosensitive emulsion 11 is exposed to a predetermined subject matter to form therein a latent image of said subject matter. The exposed emulsion is superposed on image-receiving layer 13 and the photographic processing composition 12 spread between the opposed surfaces of said emulsion 1i and said image-receiving layer 13. Reagents permeate into the photosensitive emulsion ll, developing the latent image contained therein and forming a soluble silver complex of unexposed silver halide. Soluble silver complex is transported from photosensitive emulsion layer 11, at least in part, by imbibition, to print-receiving stratum l3 and the silver of the complex is precipitated thereon and/or therein to provide the desired positive image formation. The laminate formed by the spreading of the processing composition as layer 12 between photosensitive emulsion layer 11 and print-receiving layer 13 is kept intact for approximately 12 to 1 /2 minutes, preferably 1 minute, and at the termination of this time interval the print-receiving layer 13 is dissociated from photosensitive emulsion lll as, for example, by manual stripping.

A further transfer process of the present invention for the production of positive silver prints is illustrated in FIG. 2 and comprises a spreader sheet 15, a layer of relatively viscous processin-s composition 1'2, a photosensitive gelatin emulsion layer 11 superposed on imagereceiving layer 13 which is, in turn, superposed on a support layer 14. As stated in connection with the description of FIGURE 1, image-receiving layer 13 preferably contains silver precipitating nuclei and support layer l4 may comprise either an opaque or transparent material.

Fluid composition layer 12 may be obtained by spreading a photographic processing composition, for example, in a manner disclosed in U.S. Patent No. 2,698,244. As disclosed in the aforementioned patent, the liquid processing composition may be disposed in a r upturable container so positioned in regard to the appropriate surface of photosensitive emulsion layer 11 that, upon compression by spreader sheet 15, a substantially uniform layer 12 of processing composition is distributed over the external surface of said photosensitive emulsion 11, with respect to image-receiving layer 13.

In carrying out the last-mentioned transfer process, the photosensitive emulsion ll. is exposed to a predetermined subject matter to form therein a latent image of said subject matter. A substantially uniform distribution of processing composition 12 is distributed on the external surface of said emulsion ill, as for example, according to the previously described procedure. Processing composlowly. Stirring was continued for one hour. The oil that separated was extracted with ether and the ether extracts combined and extracted with dilute hydrochloric acid. The acid phase was neutralized with 3 N Na C0 and the oil taken up in ether. The ether extract was dried over MgSO the solvent removed, and the residue distilled. The product boiled at 102 to 105 C. at 0.25 mm. pressure. [Yield was 50 to 60%.]

B. PREPARATION OF 2-ETHOXY-G-METHYL-PHENOL 21.5 grams of 6-(dimethylarninomethyl)-2-ethoxyphenol was dissolved in 150 cc. of absolute ethanol and reduced at 175 C. and an initial pressure of 1800 psi. for 6 hours in the presence of 2 grams of copper chromite catalyst. The catlyst was filtered 01% and the filtrate concentrated to approximately 50 cc. The filtrate was diluted with 200 cc. of water and acidified with hydrochloric acid. The oil which separated was extracted with ether and washed with water until a neutral pH was attained. The ether solution was dried over CaCl the solvent removed, and the residue distilled. The product boiled at 97.5 C. at mm. pressure [Yield was ca. 70%.] Reduction may also be carried out at room temperature and low pressure employing a palladium on barium sulfate catalyst in an ethanol solution.

C. PREPARATION OF 4AMINO-2-ETHOXY-6-METHYL PHENOL Sulfanilic acid was coupled into 2-ethoxy-6-methylphenol to provide 2-ethoxy-6-methyl-4-sulfopl1enylazophenol which is reduced with sodium hydrosulfite to provide the desired product exhibiting a melting point at 73 C.

EXAMPLE 3 Syntheses of 4-Amino-Z-Methoxy-Phenol, 4-Amz'no-2- Etlzoxy-Phenol, 4-Am1'lz0..-Propoxy-Phen0l, 4-Ali'lill0- Z-Butoxy-Phenol, 4-Amilz0-2,6-Dimethyl-Phenol, 4- Amin0-2-Methyl-6-Pr0pyl-Phen0I, zmd 4-Amz'n0-2,6- Dimetlzoxy-P/renol The aforementioned compounds were synthesized by coupling sulfanilic acid into the appropriate phenol and reducing the resultant alkyl and/or alkoxy substituted 4-sulfopheny lazo-phenol with sodium hydrosulfite.

4-amino-2-methoxy-pheno1 exhibited a melting point at 177 C.

4-amino-2-propoxy-phenol exhibited a melting point at 250 to 260 C.

4-an1ino-2-butoxy-phenol exhibited a melting point at 172 to 174 C.

4-amino-2,6-dimethyl-phenol exhibited a melting point at 281 to 282 C.

4-amino-2-methyl-6-propyl-phenol exhibited a melting point at 233 to 240 C.

4-amino-2,6-dimethoxy-phenol point at 232 C.

An alternative synthesis for the compounds of the present invention is to couple 2,5-dichioroaniline into the appropriate phenol, reduce the resultant product catalytically, and separate the desired product by the addition of one equivalent of hydrochloric acid followed by ether.

The novel silver halide developing agents of the present invention are useful in conventional black-and-white development and in difiusion transfer processes, both dye and silver. Examples of such processes are disclosed in U.S. Patents Nos. 2,543,181 and 2,662,822 to Edwin H. Land.

In particular, the novel silver halide developing agents of the present invention are highly useful in so-called high speed diffusion transfer processes wherein high quality silver transfer prints are obtained from a silver halide emulsion which has been substantially underexposed in relation to its A.S.A. rating. Such an exposure provides a latent image having a density gradient confined to the low exposure or toe region of the ne ative maa terials characteristic curve. Processes of this type are exhibited a meltinr t3 disclosed in the copending application of Edwin H. Land et a1., Serial No. 564,492, filed February 9, 1956.

The speed of a photosensitive material comprises generally an empirically derived relative measurement which may be defined as a value representing the reciprocal of the exposure required to produce a given result. Any precise definition of speed, therefore, is based upon the selection of a particular result as the standard reference point. A precise quantitative measure of speed has been developed from the work of L. A. Jones et al., as reported in Mees, The Theory of the Photographic Process, The Macmillan Compan New York, 1944, chapters XIX and XXII. This work suggested a system in which negative sensitive materials are assigned a speed that is in 'erms of the exposure required to give a negative image from which a positive print of specified quality can be produced.

Based on this work, The American Standards Association, Incorporated, has established standards for rating sensitive materials for speed. Under such standards, emulsion speed is considered as a value inversely proportional to the minimum exposure which must be incident upon the negative material, from the scene element of minimum brightness in which detail is visible, in order that a print of excellent quality can be made from the resultant negative. These standards specify techniques for plotting the characteristic H. & D. curve of a negative material, that is, the curve relating the logarithm of the original exposure of the negative to density in said negative. The value of speed derived from the standard characteristic curve so determined is specified as equal to the reciprocal of the exposure, E, on the characteristic curve at which the slope is 0.3 times the average slope for a log exposure range of 1.5 of which E is the minimum exposure. The precise method for determining speed in this manner is described in detail in the publication of The American Standards Association, Incorporated, PH 2.54954, and titled American Standard Method for Determining Photographic Speed and Exposure Index.

The A.S.A. speed rating is to be distinguished from hat is termed the A.S.A. exposure index, for use with exposure meters and calculators. The A.S.A. exposure index is determined by the formula: A.S.A. exposure index=A.S.A. speed/4. The exposure index so obtained indicates generally the correct exposure rating to which an A.S.A. calibrated exposure meter must be set in order that it give correct exposure data for producing pictures of satisfactory high quality.

The A.S.A. speed rating is to be further distinguished from what may be termed diifusion transfer process exposure index. In such processes, the exposure index may be based on a curve relating original exposure of the negative to the density in the resultant positive. It has been found experimentally that the diffusion transfer exposure index of a silver transfer process may be determined by plotting a characteristic curve of the reflection density of the positive as a function of the log exposure of the negative, determining the exposure in metercandle-seconds (m.c.s.) at the point on this curve corresponding to a density of 0.50, and dividing the constant, 4.0, by the exposure so determined. The exposure index so obtained indicates generally the correct exposure rating of a silver transfer process to which an exposure meter, calibrated to the A.S.A. exposure index, must be set in order that it give correct exposure data for producing transfer prints of satisfactory high quality, and is sometimes referred to as the equivalent A.S.A. exposure index.

Both the A.S.A. exposure index fer exposure index can be judged or rated according to sensitometric criteria with exposure, that is the luminance flux reaching a unit area of the photosensitive surface, being measured in m.c.s. The equivalence of the foregoing methods of determining rated A.S.A. exposure and the diffusion transsition reagents permeate into photosensitive emulsion 12, developing the latent image contained therein according to the point-to-point degree of exposure thereof. Substantially contemporaneous with the development of the latent image, an imagewise distribution of soluble silver complex is formed from unexposed and undeveloped silver halide within said emulsion. At least part of said silver complex, solubilized, is transferred, by imbibition, to print-receiving stratum 13. The transferred silver complexes are reacted therein to provide a positive, reversed image of the latent image. Subsequent to formation of the positive image in image-receiving layer 13, dissociation of said layer from emulsion layer 11 may be effected.

Where desired, the image-receiving layer 13 may be dissociated from emulsion layer 11 by stripping the emulsion from the surface thereof. A conventional stripping layer may be provided to facilitate separation of emulsion layer 11 from image-receiving layer 13 subsequent to transfer processing. Sufficient abrasion-resistant properties may be provided to image-receiving layer 13 as to alleviate any necessity of subsequently overcoating the external surface of said image-receiving layer 13 with a transparent abrasion-resistant water-soluble plastic to prevent subsequent laceration and resultant degradation of the positive image. Image-receiving layer 13 may also comprise sufiicient integral dimensional stability as to alleviate the necessity of a separate support layer 14.

In the last-mentioned processes, spreading of the liquid processing composition on the external surface of photosensitive emulsion layer 11 is preferably effected by rupture of a suitably positioned frangible container and distribution of its processing composition contents by means of a converted cellulose acetate spreader sheet, that is, a cellulose acetate sheet the surface of which has been converted to cellulose. When employed, the converted cellulose acetate spreader sheet may exhibit an adhesive capacity for the processing composition in excess of the adhesive capacity exhibited by the photosensitive emulsion. A means is thus provided for effecting dissociation of the processing composition from contact with the photosensitive emulsion, subsequent to image formation, by dissociating the spreader sheets from its proximate relationship to the external emulsion surface.

It will be apparent that the facility with which the photosensitive emulsion layer is dissociated from contact with the print-receiving layer may be increased by pro viding a conventional stripping layer interposed between said emulsion and said print-receiving layer. The stripping layer may be coated on the surface of the printreceiving element and a photosensitive emulsion thereafter coated on the external surface of said stripping layer.

While distribution of the processing composition in diffusion transfer processes has been described utilizing a frangible container, it will be apparent that said container provides a convenient means of distributing the liquid processing composition to permit the processing to be efifected within a suitable camera apparatus. The diffusion transfer processes of this invention may be otherwise effected. For example, a photosensitive element, after exposing a suitable apparatus and while preventing further exposure thereafter to actinic radiation, may be removed from such apparatus and permeated with the liquid processing composition as, for example, by coating, spraying, flowing etc., the composition on said photosensitive element or otherwise wetting said element with a composition, following which the permeated, exposed, photosensitive element, still without additional exposure to actinic radiation, is brought into contact with the image-receiving element for image formation in the manner heretofore described.

The rupturable containers may be constructed in accordance with the disclosures set forth in U.S. Patent No. 2,634,886. Containers of this type are generally constructed from a blank comprising a flexible, deformable,

three-ply sheet material comprising, respectively, an outer layer of kraft paper, a layer of metal foil and an inner layer or liner of a thermoplastic resin. The container blank is folded upon itself such as to provide a fluid-containing cavity and a container exhibiting a sealed passage adjacent to an edge thereof which may be substantially uniformly unsealed throughout a predetermined length of the seal passage upon application of stress to the container. The passage may be formed by the utilization of differential adhesion.

As previously noted, the print-receiving stratum preferably contains silver precipitating agents or nuclei, whose presence during the transfer process has a desirable effect on the amount and character of the silver precipitated during positive print formation. Examples of such silver precipitating agents are the metallic sulfides and selenides, thiooxalates, and thioacetamides, and colloidal metals disclosed in U.S. Patent No. 2,698,237. It is also desirable, as disclosed in that patent, to provide, as the vehicle for the silver precipitating agents, a macroscopically continuous film that consists of submacroscopic agglomerates of minute particles of a suitable water-insoluble, inorganic, preferably siliceous, material such as silica aerogel. The use of such a vehicle for the precipitating agents tends to aggregate the silver that is precipitated into its most effective condition for print formation.

Silver halide solvents suitable for incorporation in the processing composition include conventional fixing agents such as sodium thiosulfate, sodium thiocyanate, ammonium thiosulfate, or associations of cyclic imides and nitrogenous bases such as associations of barbiturates or uracils and ammonia or amines. Of these, the conventional fixing agents specified are preferred. Preferably, the solution also contains a film-forming material such as a water-soluble plastic, starch or gum imparting a viscosity of from 1000 to 200,000 centipoises at a temperature of 20 C. in order to permit the solution to be readily controlled during and after spreading.

It Will be apparent that the relative proportions of the agents of the developer composition set forth herein may be altered to suit the requirements of the operator. Thus, it is within the scope of this invention to modify the herein described developing compositions by the substitution of preservatives, alkalies, silver halide solvents, etc., other than those specifically mentioned. When desirable, it is also contemplated to include, in the developing composition, components such as restrainers, accelerators, etc. Similarly, the concentration of developing agent may be varied over a wide range and when desirable the developing agent may be disposed in the photosensitive element prior to the exposure of the emulsion. The devevloping agent may be disposed in a separate permeable layer of the photosensitive element and/or in the photosensitive emulsion.

The emulsion support layer designated in the drawing as 10 may comprise any of the various types of conventional rigid or flexible supports, for example, glass, paper, metal, and polymeric films of both the synthetic types and those derived from naturally occurring products.

The photosensitive emulsion stratum may comprise a commercially available silver halide gelatin emulsion such as sold by Eastman Kodak Company under the trade names Microfile, Spectrum Analysis, Contrast Process, SXX Aero Recon, Verichrome, Royal Pan, Royal X Pan, or Tri X Pan, or sold by E. I. du Pont under the trade names Fine Grain Pan, High Speed Pan, Arrow Pan, or Superior 3, or sold by Ansco under the trade name Triple S Pan, or sold by Gevaert under the trade name Gevapan.

Of the develop ng agents of the present invention, compounds wherein both R and R are each alkoxy groups containing from 1 to 4 carbon atoms and compounds wherein R comprises an alkyl containing from 1 to 4 carbon and R comprises an alkoxy group containing from 1 to 4 carbon atoms and in each case wherein R and R together comprise not more than 5 carbon atoms, possess specific and unexpected advantages. These compounds are characterized by unexpected and exceptional high process speeds when employed in diffusion transfer processes.

The compuonds of the present invention may also be used in small quantities with other silver halide developers, for example, hydroquinone or one of its derivatives, to produce high speed prints of exceptional quality by diffusion transfer processes.

The present invention will be illustrated in greater detail in conjunction with the following specific examples which set out representative use of the novel silver halide developing agents of this invention in high speed diffusion transfer processes, which however are not limited to the details therein set forth and are intended to be illustrative only.

The indicated developing agents employed and the results obtained in the specific examples are hereinafter set forth in tabular form. (Specific examples employing metol and hydroquinone, respectively, have been reported for the purpose of providing comparative data.)

A silver iodobromide emulsion having the designated A. S.A. exposure index is exposed to a predetermined subject through a stop which gives rise to the indicated diffusion transfer exposure index, advanced in superposed relationship with an image-receiving element, comprising a silver-receptive stratum containing silver precipitating nuclei dispersed in a matrix of colloidal silica coated on a water-impervious base according to the practice described in U.S. Patent 2,823,122, issued to Edwin H. Land on February 11, 1958, between a pair of pressure-applying rollers to spread a processing composition comp-rising:

Water cc 398 Carboxymethyl cellulose (high viscosity) grams 15.25 Sodium sulfite do- 25.6 Sodium hydroxide do 15.2 Sodium thiosulfate do 5.4 -nitrobenzimidazole do 0.5

9:! therefore, be that required to reproduce the minimum diffcrence existing in the shadow regions of the object by means of some minimum density difference in the resulting image.

When the novel developing agents of this invention are used in high speed diffusion transfer processes, the region of the ASA. characteristic curve of the negative used in accordance with the present invention lies at a relatively low exposure level and corresponds to an exposure gradient predominantly below approximately 0.015 mes. Ordinarily, the fog level in such a case is at a point on the characteristic curve that corresponds to an exposure gradient predominantly above approximately 0.005 m.c.s.

As used herein and in the above table, the shoulder speed is the minimum amount of exposure in metercandle-seconds which can be used to expose the negative emulsion and give a transfer image in which there is the minimum contrast which the eye can distinguish, i.e., there is visible detail in the shadow regions of the transfer image. This exposure level is determined at the point on the shoulder portion of the previously described characteristic curve of the positive transfer image where the slope is 0.4.

As illustrated in the aforementioned specific examples the photosensitive emulsions of the present processes are underexposed in relation to their respective A.\S.A. exposure index to produce therein a weak latent image having an exposure gradient predominantly in the toe region of the A.S.A. density versus log exposure curve of the photosensitive emulsion. The emulsion is therefore exposed to produce a latent image lying in the toe region of the A.S.A. characteristic curve for the negative emulsion such that, by the standard A.S.A. development method, it would be impractical to develop the emulsion such as to provide a useful conventional negative image. By means of the compositions, products and processes of the present invention, one may advantageously employ a photosensitive emulsion having a stated A.S.A. exposure inlex and provide said emuision with an effective exposure that ordinarily would require a photosensitive emulsion having a higher A..S.A. exposure index to provide an acceptable positive print resultant therefrom.

With conventional developing practices, good negatives can be obtained only from an emulsion that has been SlllfiCiCllllY exposed within the range of exposures specified for the emulsion. Undcrexposed emulsions result in a negative having only an image from which it is impractical to obtain a satisfactory print by conventional processes.

Concentration Diffusion Emulsion (grauis/ Imbibition Density Density Transfer 1.5.11. Shoulder Compound 10 cc. proe- Time (maximum) (minimum) Slope Exposure Exposure Speed ossing (minutes) Index index (n1.c.s.)

composition) 0. 4 1 1. 40 O. 01 2. 02 2, 000 200 0.000 10 0. 4 1 0. 82 0.01 0. 00 9,000 0a. 300 0. 00022 0. 4 1 1. 07 0.01 1. 18 100 200 0. 00030 0. 4 1 1. 31 0. 03 0. 06 180 Ca. 800 0. 0024 0. 4 2 1.14 0.00 1. 54 12, 100 0:1..800 0. 00015 0. 4 1 1. 12 0.01 O. 79 3, $40 ca. 800 0. 00015 0. 2 2 1. 36 O. 00 1. 74 3, 000 200 0. 00016 0. 4 2 0. 99 0.00 1. 23 15, 100 ca. 800 0. 000074 0. 4 1 1. 23 0.10 O. 88 1,150 On. 800 0. 00051 0. 4 1 1.18 0. 02 0. 73 l, 900 ca. 800 0. 000077 0. 4 1 1. 30 0. 00 1. 08 5. 500 (3:1. 800 0. 000080 0. 4 2 1. 51 0.00 1. 09 13, 600 (:a. 80 0. 000004 It will be noted from the tabular results set forth above The present 1nvent1on obviates the problem of conthat compound 9, 4-arnino-2,6-dirnethyl-phenol, exhibits exceptionally high speed in comparison with compound 5, 4-amino-2-methyl-6-propyl-phenol, both of which compounds comprise bis-aikyl substituted p-amino-phenols. It will be further noted that compound 5 exhibits a higher minimum density.

The chief function of a photographic negative material as used in pictorial photography is to reproduce as density differences the luminance differences existing in the object photographed. The minimurn useful exposure will,

structing a satisfactory negative from an underexposed emulsion, for example, by intensification, hyperscnsitization, latensification techniques, so as to obtain a satisfactory positive print. In addition, the present invention provides satisfactory positive images from both underexposed and adequately exposed conventional silver halide photosensitive emulsions. As previously mentioned, a convenient measure of the amplification of image development, obtained according to the present disclosure, over the results obtained from conventional development prac- 13 tices, is in terms of increase in the speed or quantum excitation sensitivity of the emulsion as indicated by the results previously set forth, over the normal specified speed of the same emulsion as determined by the results of standard development practice.

Since certain changes may be made in the above products, processes and compositions without departing from the scope of the invention herein involved, it is intended that all matter contained in the above description or shown in the accompanying drawing shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. A photographic process which comprises the steps of underexposing a photosensitive silver halide emulsion with respect to its A.S.A. exposure index to produce therein a latent image having an exposure gradient in the toe region of the A.S.A. density versus log exposure curve of said silver halide emulsion, developing said emulsion with an aqueous halide emulsion, developing said emulsion with an aqueous alkaline solution comprising a silver halide developing agent of the formula:

wherein R is selected from the group consisting of alkyl and alkoxy groups comprising from 1 to .4 carbon atoms; R is an alkoxy group comprising from 1 to.4 carbon atoms; and both R and R taken together comprise not more than 5 carbon atoms; contacting unreduced and undeveloped silver halide therein with a silver halide solvent to form an imagewise distribution of soluble silver complex, transferring at'least part of said imagewi-se distribution, by im-bibition, to a contiguous image-receiving material containing silver precipitating agents, and thereby effecting precipitation of transferred soluble silver complex to provide a positive silver print of full pictorial density on said imagereceiving material.

2. A process as defined in claim 1, wherein said developing agent is 4-amino-2 methoxy-6-methyl-phenol.

3. A process as defined in claim 1, wherein said developing agent is 4-amino-2,6-dimethoxy-phenol.

4. A process as defined in claim 1, wherein said developing agent is 4-amino-2-ethoxy-fi-methyl-phenol.

5. The photographic process which comprises the steps of selectively exposing a photosensitive gelatino silver halide emulsion with a luminance flux incident thereon not substantially in excess of 0.015 meter-candle-seconds; developing exposed silver halide in said photosensitive emulsion with an aqueous alkaline solution containing a silver hailde developing agent of the formula:

wherein R is selected from the group consisting of alkyl and alkoxy groups comprising from 1 to 4 carbon atoms; R is an alkoxy group comprising from 1 to 4 carbon atoms; and both R and R taken together comprise not more than 5 carbon atoms; and a silver halide solvent;

. 14 contacting unexposed and undeveloped silver halide therein with said silver halide solvent and forming thereby an imagewise distribution of a soluble silver complex in the unexposed areas of said emulsion, as a function of the point-to-point degree of exposure thereof; transferring from said emulsion, at least in part, by imbibition, said imagewise distribution of soluble silver'complex to a print-receiving layer, containing silver precipitating nuclei, in superposed relationshi to said emulsion; and there precipitating silver complex to provide thereby a reversed positive, iull scale silver print of said latent image. 6. A photographic process which comprises the steps of exposing a photosensitive gelatino silver halide emulsion with a light flux incident thereon predominantly within the exposure range delineated by the toe region of said emulsions "characteristic H. and D. curve, determined according to A.S.A. Standard PH 2.5-1954; developing exposed silver halide in said photosensitive emulsion with an aqueous alkaline solution of a silver halide developing agent of the formula:

I NH:

wherein R is selected from the group consisting of alkyl and alkoxy groups comprising from 1 to 4 carbon atoms; R is an alkoxy group comprising from 1 to 4 carbon atoms; and both R and R taken together comp-rise not more than 5 carbon atoms; contacting undeveloped silver halide with a silver halide solvent and forming thereby an imagewise distribution of soluble silver complex in the unexposed areas of said emulsion; transferring from said emulsion, at least in part, said imagewise distribution of soluble silver complex to a print-receiving element, containing silver precipitating agents, in superposed relationship to said emulsion; and precipitating said silver complex to provide thereby a reversed, positive print possessing a characteristic curve with a slope greater than the slope of said H. and D. curve, said positive prints characteristic curve determined by plotting the reflection density of the positive print as a function of the log exposure of the negative.

References Cited in the tile of this patent UNITED STATES PATENTS 2,692,830 Rogers et a1. Oct. 26, 1954 2,740,717 Yutzy et al Apr. 3, 1956 2,909,430 Rogers Oct. 20, 1959 3,039,869 Laud June 19, 1962 OTHER REFERENCES The British Journal of Photography, vol. 39 (1892), pp. 440-1.

Clerc: Photography Theory and Practice, 2nd Ed., 1937, Pitman and Sons, London, p. 253.

McOmie et al.: Journal of the Chemical Society (London) (1955), page 2620.

U.S. Camera, July 1949, pages 58, 59, How to Multiply Your Film Speed 25 Times.

Mees: The Theory of the Photographic Process, 1954, pages 54043, 546, 547 and 563.

G-lafkides, Photographic Chemistry, Fountain Press, London (1958), pages 1'18-119.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No, 3,108,001 October 22, 1963 Milton Green It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 1, line 21, for "halid" read halide line 62, for "strutum" read stratum same column 1, line 68, for "unsually" read unusually column 3, line 73, for "copening" read copending column 4, line 35, for "4 AMINO2METHOXY6PHENOL"' read 4--AMINO-2METHOXY-6 METHYL-PHENOL line 50, for "vacumn" read vacuum column 5, line 1 1, for "catlyst read catalyst column 7, line 54, for "lever" read layer column 9, line 43, for "sheets" read sheet column 10, line 52, for "devevloping" read developing line 74, after "carbon" insert atoms column 11, line 6, for "compuonds" read compounds line 31, for "U05. Patent 2,823,122" read UOS, Patent No, 2,823,122 columns 11 and 12, in the table, ninth column, line 3 thereof, for "0.00030 read 0.0030 column 12, line 37, for "inlex" read index column 13, lines 18 and 19, strike out "developing said emulsion with an aqueous halide emulsion,"; line 55, for

"hailde" read halide column 14, line 12, for "A" read The line 50, for "Rogers et al." read Land same column 14, line 53, for "Land" read Rogers et a1,

Signed and sealed this 12th day of May 1964,

(SEAL) Attest;

ERNEST W. SWIDER EDWARD J, BRENNER Attesting Officer Commissioner of Patents 

1. A PHOTOGRAPHIC PROCESS WHICH COMPRISES THE STEPS OF UNDEREXPOSING A PHOTOSENSITIVE SILVER HALIDE EMULSION WITH RESPECT TO ITS A.S.A. EXPOSURE INDEX TO PRODUCE THEREIN A LATENT IMAGE HAVING AN EXPOSURE GRADIENT IN THE TOE REGION OF THE A.S.A. DENSITY VERSUS LOG EXPOSURE CURVE OF SAID SILVER HALIDE EMULSION, DEVELOPING SAID EMULSION WITH AN AQUEOUS HALIDE EMULSION, DEVELOPING SAID EMULSION WITH AN AQUEOUS ALKALINE SOLUTION COMPRISING A SILVER HALIDE DEVELOPING AGENT OF THE FORMULA: 